def run():
    # 空变量，存储的作用data始终为空
    data =""
    # 返回，启动生成器的时候调用
    r = yield data
    # r=a
    print(1, r, data)
    r = yield data
    # r=b
    print(2, r, data)
    r = yield data
    # r = c
    print(3, r, data)
    r = yield data


m = run()
# 启动m
print(m.send(None))
print(m.send("a"))
print(m.send("b"))
print(m.send("c"))
print("************")